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2.2.4.1. GeoGebra link
Use the mouse to zoom in and out of the cone and to turn it.
Move point A along the generatrix of the conical surface with a mouse, or use the animation button and watch how the location of point A on the cone surface changes.
Turn the cone to see orthogonal projections of point A in different positions.
2.2.4.2. GeoGebra link
Use the mouse to zoom in and out of the cone and rotate it.
Use the animation button and watch how the lateral surface of the cone is developed and how the position of points A and B changes.
Note that the net of the cone is a sector of a circle whose radius is equal to the length of the generatrix of the lateral surface of the cone.
If you use orthogonal projections to draw a net of the cone, then you need to measure the length of the generatrix either in the right or in the left extreme position - only this length is original!
2.2.4.3
Watch a video - below on the left on how polyhedrons - pyramids are used to replace the shape of rotation - a cone.
Moreover, the pyramid is smaller or located in a cone, while its edges belong to the lateral surface of the cone - the pyramid is inscribed in the cone.
Or the pyramid is larger than the cone, and the lateral surface of the cone touches the sides of the pyramid - the pyramid is circumscribed around the cone.
Use the sliders or the animation button - below on the right and see how the cone and pyramid surfaces are getting.
Compare the results and, if necessary, use one or another method to construct a net drawing.
2.2.4.4. Watch the video on how to build an axonometric projection of a cone.
To draw its base, you need to build an oval.
To draw a conical surface, you need to use tangent lines to the arcs of the oval from the top point.
2.2.4.5. To fix the information received, check how well the knowledge gained about the cone and its net will help to answer the questions of the next exercise.
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